Water Treatment "Part 20": UV-based Disinfection Method.
The fact that this method doesn't require chemicals or produce hazardous substances, unlike chlorine disinfection, is one of its most significant characteristics. Additionally, it is simple to use, and the investment is not too expensive. This method also has some drawbacks, given that its disinfecting effect cannot be maintained outside of the transit region, in addition, the water used for this method of disinfection needs to be very pure.
This operation is based on the entry of UV light into the aqueous medium, whereby the medium's live cells are exposed to UV light.
Ultraviolet radiation possesses electromagnetic radiation that includes a range of wavelengths between 10 to 400 nm, with a frequency range between 800 and 30,000 terahertz (THz). These rays have a photochemical effect represented in the following:
- At wavelengths up to 185 nm, converting oxygen into ozone.
- At wavelengths between 200 and 280 nm, the decomposition of small organic particles.
Cutaway model of UV disinfection unit used in NEWater water treatment plants
The imbalance that UV radiation generates in a live cell's chemical makeup is what causes it to have a disinfecting effect. At a wavelength of 257 nanometres, the DNA absorbs the most UV light, making this the wavelength where disinfection is most effective. The quantity of radiation that a living cell absorbs determines whether it is destroyed or inhibited, and the disinfecting process keeps the cells alive but prevents them from reproducing, leading to their eventual demise.
Beer–Lambert law:
"A minimum of 25,000 microwatts per second per square centimetre of radiation should be used to disinfect water."
The Baer Lambert law enables the computation of energy and considers a variety of energy-related coefficients, including:
The power of the lamp (watts), the surface (m²), the absorption coefficient of radiation in the liquid, the thickness of the water that the radiation crosses is estimated (m), the time of exposure to radiation per unit size (s). The amount of exposure D is calculated in joules per square metre:
D= P/S × exp (- K Y) × T
References:
- [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]
- Taparhudee, Wara (2002). "Applications of Paddle Wheel Aerators and Diffused-Air System in Closed Cycle Shrimp Farm System" (PDF). Witthayasan Kasetsart (Sakha Witthayasat). 36: 408–419. Retrieved 26 April 2020.
- Unsafe water kills more people than war, Ban says on World Day". UN News. 22 March 2010. Retrieved 10 May 2018
- Raymond Desjardins- Livre: Le traitement des eaux- 2éme edition- Ecole Polytechnique de Montréal- 1997- ISBN 2-553-00643-8
- Drinking Water Treatment- EDX- Delft University of Technology.
- Book- Drinking Water: Principles and Practices- by Hans J C Van Dijk (Author), Jasper Q J C Verberk (Author), Peter J De Moel.